Abrasive disc



J. E. CREAN ABRASIVE DI SC June I, 1965 Filed April 4, 1962 FIG.

FIG.

INVENTOR. JOHN E. CREAN ATTORNEY United States Patent 3,186,135 ABRASIVEDISC John E. Crean, Willowdale, Ontario, Canada, assignor to TheCarborundurn Company, Niagara Falls, N.Y., a corporation of DelawareFiled Apr. 4, 1962, Ser. No. 184,977

2 Claims. (Cl. 51--394) This invention relates generally to an abrasivedisc and more particularly to an abrasive disc of noncircularconfiguration which has rounded projections extending radiallytherefrom. V

Abrasive discs are used for grinding, polishing and finishing metallicsurfaces. The discs are rotated in a circular fashion and the abrasivesurface of the disc is held against the metallic surface. It has beenfound that abrasive discs of noncircular configuration are in manyrespects superior to abrasive discs having a circular con figuration.-This'is especially true where the metallic surfaces are curved. The dischaving a noncircular configuration with the projections extendingradially therefrom is self-cleaning in that the material, eitherdislodged abrasive or metal particles dislodged by the main centralportion of the disc, is discharged from beneath the disc between theradial projections. When compared with a disc having a circularconfiguration, the dislodged material cannot be discharged from beneaththe disc until it is conveyed beyond the circumferential edge of thedisc. It is also believed that the accumulation of dislodged abrasiveand metallic particles along the peripheral edge of the disc causesirregular finishing of the metallic surface. The abrasive disc with anoncircular configuration and radial projections minimizes theaccumulation of the dislodged material along the peripheral edge of thedisc and provides a more uniform finish to the metallic surface.

In the past, the abrasive discs having a noncircular configuration allhad peaked projections extending radially therefrom. The peakedprojections had sharp corners so that the peripheral edge of theabrasive disc comprised a series of straight line linear edges joined toeach other at the angular peaked portion. Some of the discs wererectangular in configuration and others were; octagonal inconfiguration. An octagonal disc with the sharp peaked projections isillustrated in Patent No. 2,746,216, granted on May 22, 1956, andentitled Sanding Attachment.

Although the disc having a noncircular configuration and sharp peakedprojections is superior to an abrasive disc of circular configurationfor certain applications, it has been discovered that the use of theabrasive disc with the sharp corners is limited when the disc is used onmetallic surfaces having rough jagged edges and when used on metallicsurfaces with sharp angular portions.

The sharp corners of the disc have a tendency to snag on the jaggededges of the metal and break or tear the disc. The sharp corners of thedisc have a tendency to break down after a short period of use when theabrasive disc with sharp corners is used on medium rough edged material.This reduces the useful life of the abrasive discs and results inunnecessary expense in the grinding or polishing operation. When anabrasive disc having sharp corners is used on an angular surface, thatis, a surface having a substantially horizontal portion and anupstanding portion, the sharp corners tend to snag on the upstandingportion and break or tear the disc. This presents a difficult problem ingrinding or polishing the surface at the angular juncture of thehorizontal portion and the upstanding portion.

I have discovered by rounding off the sharp corners of the abrasive discthat I am able to retain the advantageous features of an abrasive dischaving a noncircular con- I figuration; and yet eliminate the problemsheretofore discussed. I have found by rounding olf the sharp corners andproviding a smooth curved projecting portion that I am able to increasethe useful life of the abrasive disc. The abrasive disc with smoothcurved projecting tion with curved projections extending radiallytherefrom.

Another object of this invention is to provide an abrasive disc ofnoncircular configuration and rounded corners that has increased lifeand is suitable for use on material having jagged edges.

Another object of this invention is to provide an abrasive disc having agenerally octagonal configuration with rounded corners.

With the above and other objects in view, which will appear as thedescription proceeds, the features of the invention reside in thedetails of construction hereinafter described and claimed, it beingunderstood that changes in the precise embodiments of the invention maybe made without departing from the spirit of the invention.

FIGURE 1 is a view in plan of one embodiment of my abrasive disc.

' FIGURE 2 is a View in section taken along the lines 11-11 of FIGURE 1.

Referring particularly to FIGURES 1 and 2, there is illustrated oneembodiment of my abrasive disc generally designated by the numeral 10.The abrasive disc 10 is illustrated as having a cellulosic backing 12having a surface 14 onto which is bonded a layer of grit 16. The grit 16may be any suitable abrasive such as carbide or aluminum oxide grains ofany desired grit size. The backing 12 may also be a vulcanized fibrousmaterial laminated to a layer of cloth with a phenol formaldehyde resinor the like. The layer of abrasive 16 is bonded to the backing 12 bymeans of a suitable bonding material, for example a phenol formaldehyderesin. It should be understood that any suitable backing and abrasivemay be employed Without departing from the scope of this invention.

The abrasive disc 10 has a central shaft receiving aperture 18therethrough and a central circular portion 39. The circumferentialboundary of the central portion 30 is illustrated by the dotted line 32.It should be understood that in the embodiment illustrated in FIGURE 1the designation of the central portion 30 with its circumferentialboundary designated by slotted line 32 is not intended to indicate thatthe central portion is formed separately of the noncircular projections.The designation of the circular portion 30 is for convenience only tomore clearly point out the improved shape of the peripheral edge portionof the disc illustrated in FIGURE 1. Extending radially outwardly fromthe disc central circular portion 30 are a plurality of roundedprojections or curved lobe portions 34. The adjacent lobe portions 34are joined by a curved portion 36 so that the peripheral edge portion ofdisc 10 may be considered as having a rosette shape. The portions 34 maybe considered as being curved portions extending radially outwardly ofthe central circular portion 30 and the curved edge portions 36 may beconsidered as curved portions extending radially inwardly toward thecentral circular portion 30.

The peripheral edge portion of disc is sinusoidal in shape in that aregular curve similar to a sine wave would be formed if the peripheraledge of the disc 10 were projected on a flat surface. I

It has been found by employing disc 10 on rough edged material that thediscs are less likely to snag or break than discs having sharp corners.In finishing material that has sharp angles, it has been found that theperipheral edge of the disc herein described does not snag on theupwardly extending portion of the material as the material adjacent theangular portion is finished. With discs having sharp corners the sharpcorner portions have a tendency to snag on the upwardy extending portionof the metal and break or tear. It is also now possible with theabrasive discs herein described to provide a smoother finish adjacentangular projections on the material being finished.

According to the provisions of the patent statutes, I have explained theprinciple, preferred construction, and mode of operation of my inventionand have illustrated and described what I now consider to represent itsbest embodiments. However, I desire to have it understood that, withinthe scope of the appended claims, the invention may be practicedotherwise than as specifically illustrated and described.

I claim:

1. An abrasive disc which comprises a continuous, nonsegmented basemember and abrasive grain bonded to one surface of said base member,said disc having a central circular portion and a curved peripheral edgeportion,

said curved peripheral edge portion being formed of a plurality ofradially inwardly curved edge portions and a plurality of radiallyoutwardly curved edge portions, said radially inwardly curved edgeportions forming a smooth junction between said radially outwardlycurved edge portions so that said peripheral edge portion issubstantially free of sharp pointed corners.

2. A disc of abrasive material having a continuous, nonsegmented basemember and abrasive grain bonded to one surface of said base member,said disc being suitable for use on material having jagged edges, saiddisc having a circular central portion and a curved peripheral edgeportion, said curved peripheral edge portion including a plurality ofradially inwardly curved edge portions and a plurality of radiallyoutwardly curved edge portions, said curved peripheral edge portionformed of alternating inwardly curved edge portions and outwardly curvededge portions, said radially inwardly curved edge portions blending withsaid adjacent outwardly curved edge portions to form a smooth junctiontherebetween.

References Cited by the Examiner UNITED STATES PATENTS 1,216,488 2/17Pfeilfer 51-195 2,307,632 1/ 43 Meyer 51-209 2,492,143 12/49 Gipple etal. 51196 2,746,216 5/56 Hollingsworth 51195 FOREIGN PATENTS 804,7624/51 Germany.

LESTER M. SWINGLE, Primary Examiner.

FRANK H. BRONAUGH, J. SPENCER OVER- HOLSER, Examiners.

1. AN ABRASIVE DISC WHICH COMPRISES A CONTINUOUS, NONSEGMENTED BASEMEMBER AND ABRASIVE GRAIN BONDED TO ONE SURFACE OF SAID BASE MEMBER,SAID DISC HAVING A CENTRAL CIRCULAR PORTION AND A CURVED PERIPHERAL EDGEPORTION, SAID CURVED PERIPHERAL EDGE PORTION BEING FORMED OF A PLURALITYOF RADIALLY INWARDLY CURVED EDGE PORTIONS AND A PLURALITY OF RADIALLYOUTWARDLY CURVED EDGE PORTIONS, SAID